And there is nothing that can be done against it?
I'm going to try and keep this as simple as possible for the sake of things, but it'll have to be a bit technical. Also keep in mind I'm more knowledgable in the digital side of the film as I've used that far more than actual film, but here is what I've read over the years.
The short answer to your question is yes and no. Without rescanning the film elements, there is nothing they can do. With rescanning the original film elements? Possibly. Let me explain: First off, it depends on what format they shot the films in, and then the aspect ratio they shot the short films in. This will vary between every one. I'm not sure of the technical details for most of MJ's films, they've never really been discussed. From what I've read, all from the Thriller era onwards were shot on 35mm film. Off the Wall era shorts were shot on tape and Billie Jean was shot on 16mm film.
Now as they stand on the Vision DVD, the short films are either 4:3 (1.33:1) or 16:9 (1.77:1).
So starting off with tape, I believe tape was just shot in 4:3, so for the Off the Wall era films, no there is nothing we can do. You'll always have black bars when viewing them on a widescreen display.
Next off, we have 16mm, which Billie Jean was shot on for budget reasons; I'm not sure if it was standard or super 16mm film.
If it was
standard 16mm, it would be 1.37:1 which isn't much wider than 4:3. If it was shot on
super 16mm, it would be relatively close to widescreen so we could have a wider presentation (there would still be black bars on the top and bottom, but they'd be pretty small). I think Billie Jean was shot on standard 16mm but this I cannot confirm.
Here's a visual representation: Super 16mm is on the left, Standard 16mm is on the right.
Now with 35mm, it gets a teensy bit more complicated because it also depends on the type of lenses they used. To keep it really simple, from what I've read, when shooting for your standard 16:9 image (that is, "normal" widescreen and not the super wide anamorphic 'CinemaScope' aspect ratio you often seen with blockbuster films like
THIS wide), they tend to shoot in a full 4:3-like frame and then later crop it during editing or theatrical projection. This is called 'Open matte'.
You can see this demonstrated in this diagram below. Here you see the entire piece of film, the blue area represents what we see when it's cropped to the intended widescreen ratio, the green area represents what we see when it's cropped to an aspect ratio of 4:3.
Here's another, more visual, example. Although this yellow box seems to be about 2.35:1, you could still make it a bit taller and it'd be 1.85:1. The same principle still applies generally.
An actual example here can be seen with Alfred Hitchcock's Psycho (1960), the green area representing the aspect ratio that Hitchcock and his DoP intended. The area behind it is a cropped 4:3 used on some VHS release (which as you can see, they cropped in a-bit, cutting out information on the sides - just like the image above).
So my somewhat educated guess for Michael's short films is that they shot in that aspect ratio, then just cropped it to 4:3 (although I'm not sure how far they cropped in, sometimes they'll crop in a bit further as seen in the Hitchcock image). So theoretically, it is possible we could get some more information on the sides but not much, we'd still have to crop the top and bottom. This might not work well for some short films, depending on Michael, the director and the Director of Photography's intentions.
In fact, I believe Moonwalker and it's associated short films was shot like this. The Moonwalker DVD presents the film in 4:3, whereas the Blu-ray presents it in cropped 16:9, similar to the above image for Psycho. However, watching the 4:3 presentation, I did notice how the areas that were cropped out didn't offer anything important to the image, and in fact were sometimes empty or even had the edge of the set (I recall the short where Sean Lennon and the other kid dance outside the night club, you see the stone path cut off unusually). So I believe that the intended presentation of Moonwalker is actually what it is on the Blu-ray: widescreen.
I'm reminded of That 70's Show actually. It too was shot on 35mm and then presented in 4:3 (for television), but recently they have gone back and redone the whole series, rescanning all the negatives. For a more widescreen picture, they cropped some of the top and bottom, but regained information on the sides that was lost when cropping it for television. What you see here is probably what we could get for MJ's short films:
So in conclusion:
-For short films shot on tape (i.e. OTW), no there's nothing we can do.
-For short films shot on 16mm (i.e. Billie Jean), we might be able to, it depends on which kind of 16mm it was shot on.
-For short films shot on 35mm, we might be able to get some more information on the sides, but you'd have to lose information on the top and bottom.
I hope this makes sense! I'm extremely familiar with aspect ratios and the digital side of filmmaking but as I haven't had much hands on with actual film itself, I'm still relatively new to some aspects of it. However for now this seems to be my best guess